Alassane Ouattara, the internationally recognised winner of last November's presidential election, announced a one-month suspension on exports of cocoa this morning. Ouattara said anyone flouting the blockade would be considered to be "financing the illegitimate regime" of Laurent Gbagbo, the incumbent Ivory Coast leader. Gbagbo is refusing to leave office despite Ouattara being widely accepted as Ivory Coast's legitimate leader.

Ivory Coast is the world's largest supplier of cocoa, contributing around 40% of global output.

The cost of a tonne of cocoa jumped by 6.2% to $3,393 this morning, the highest level since January 2010. Cocoa prices have been rising steadily since November's election, and analysts have predicted that they could continue to escalate unless the deadlock in Ivory Coast is resolved.

Ouattara's supporters say Ivory Coast's main producers have agreed to the ban, but it is not clear whether Ouattara will succced in imposing a blanket ban. This has created confusion across the industry. Two European cocoa industry bodies said this morning that they are asking for clarification about the suspension.

"As can be expected in these circumstances, the trade issues involved in this respect are of a highly sensitive nature and will take time to resolve," said the European Cocoa Association and the Federation of Cocoa Commerce in a joint statement.

There is concern that speculation by financial traders has helped to push up food prices worldwide, creating an unsustainable bubble that makes it even harder for many in the developing world to afford to eat. Workers in the UK have also felt the impact - Burton's Foods blamed higher cocoa and wheat prices for the closure of its Wirral factory - where Wagon Wheels and Jammie Dodgers are made - with the loss of over 400 jobs.